How Do Hummingbirds
Know when to
Migrate?

When should I take down my hummingbird feeders? I still have three ruby-throated hummingbirds here every day. I love seeing them, but I don't want to tempt them to stay longer than they should. -- Sidney P., Fairfield, Iowa

I'm happy to tell you that you can leave your hummingbird feeders up as long as hummingbirds are visiting them. And then a week or so longer, just in case a straggler comes through.

You need not be afraid of causing the birds to delay their migration and get caught by winter. That isn't going to happen.

It's not the lack of food that tells a hummingbird when to go south. It's the bird's internal biological calendar, or circannual rhythms.

As the time of migration approaches, the hummingbird starts to pack on fat, which will fuel its journey. And then it gets an overwhelming urge to migrate. The biological rhythms run automatically, but they are synchronized and fine tuned by the changing day length.

The amount of food in the environment does not affect the migratory urge. In fact, the birds leave their summer home while food is still plentiful. That way, they are reasonably assured of finding more food along the way.

So your hummingbird feeder is not going to tempt the hummers to overstay their schedule. In fact, the sugar water you offer will help the hummingbirds "gas up" for their journey. Hummingbirds that are already on their way south can stop by and replenish their stores, too.

In the western United States, the Anna's hummingbird stays in much of its range year around. But most hummingbirds do go south for the winter. You might as well enjoy their visits on their way.

I always keep my feeders up for a few weeks after I stop seeing hummingbirds in the fall. I continue to change the syrup every couple of jays, to keep the feeder clean and free from mold and fermentation.

Sometimes a late hummingbird straggles by long after all the others have gone. This might be a young bird that hatched late in the season and that wasn't ready to migrate when the others left. I'm glad to be able to offer a little extra help.

A pretty feeder for hummingbirds

It attaches by two suction cups right on the window. It's easy to refill and clean. We can see our favorite birds as close as we wish!

In fact, I love to hold it in my hand when I take it out with fresh sugar water in it. The hummingbirds buzz around my head and then hover for a quick sip. I feel the vibration of the wings as it is communicated to the feeder through their bills. (Click the photo at left for 4-second QuickTime movie. )